What is the first element on the periodic table?

The story behind the answer

Hydrogen is first because the periodic table is ordered by atomic number—the number of protons in the nucleus—and hydrogen has just one. It’s the lightest, simplest atom (1 proton, usually 1 electron). By contrast, helium is 2, lithium 3, and oxygen 8.

Beyond the table, hydrogen is the most abundant element in the universe and the primary fuel of stars; in stellar fusion, hydrogen nuclei combine to form helium, powering the sun. Memory tip: “Hydrogen heads the table”—H is for “head” and “one” (H-1). If you remember that the periodic table climbs by proton count, hydrogen’s